Ma. Karam et al., A MICROWAVE POLARIMETRIC SCATTERING MODEL FOR FOREST CANOPIES BASED ON VECTOR RADIATIVE-TRANSFER THEORY, Remote sensing of environment, 53(1), 1995, pp. 16-30
A microwave polarimetric scattering model for a forest canopy is devel
oped based on the iterative solution of the vector radiative transfer
equations up to the second order. The forest canopy constituents (bran
ches, leaves, stems, and trunks) are embedded in a multi-layered mediu
m over a rough interface. The branches, stems, and trunks are modeled
as finite randomly oriented cylinders. Deciduous leaves are modeled as
randomly oriented discs and coniferous leaves are modeled as randomly
oriented needles. The vector radiative transfer equations contain non
diagonal extinction matrices that account for the difference in propag
ation constants and the attenuation rates between the vertical and hor
izontal polarizations. For a plane wave exciting the canopy, the avera
ge Mueller matrix is formulated, and then used to determine the linear
ly polarized backscattering coefficients including both the copolarize
d and cross-polarized power returns. Comparisons of the model with mea
surements from Les Landes Forest of France showed good agreements over
a wide frequency band and gave a quantitative understanding of the re
lation between the backscattering coefficients and the age of the tree
s in the forest and forest biomass.